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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4>NAME</h4><blockquote>
t_sndvudata - send a data unit from one or more noncontiguous buffers
</blockquote><h4>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="xti.h.html">xti.h</a>&gt;

int t_sndvudata(
    int fd,
    struct t_unitdata *unitdata,
    struct t_iovec *iov,
    unsigned int iovcount) 
</code>
</pre>
</blockquote><h4>DESCRIPTION</h4><blockquote>
<pre>
<P><table  bordercolor=#000000 border=1 align=center><tr valign=top><th align=center><b>Parameters</b>
<th align=center><b>Before call</b>
<th align=center><b>After call</b>
<tr valign=top><td align=left>fd
<td align=center>x
<td align=center>/
<tr valign=top><td align=left>unitdata-&gt
<td align=center>addr.maxlen
<td align=center>/
<tr valign=top><td align=left>unitdata-&gt
<td align=center>addr.len
<td align=center>x
<tr valign=top><td align=left>unitdata-&gt
<td align=center>addr.buf
<td align=center>x(x)
<tr valign=top><td align=left>unitdata-&gt
<td align=center>opt.maxlen
<td align=center>/
<tr valign=top><td align=left>unitdata-&gt
<td align=center>opt.len
<td align=center>x
<tr valign=top><td align=left>unitdata-&gt
<td align=center>opt.buf
<td align=center>?(?)
<tr valign=top><td align=left>unitdata-&gt
<td align=center>udata.maxlen
<td align=center>/
<tr valign=top><td align=left>unitdata-&gt
<td align=center>udata.len
<td align=center>/
<tr valign=top><td align=left>unitdata-&gt
<td align=center>udata.buf
<td align=center>/
<tr valign=top><td align=left>iov[0].iov_base
<td align=center>x(x)
<td align=center>=(=)
<tr valign=top><td align=left>iov[0].iov_len
<td align=center>x
<td align=center>=
<tr valign=top><td align=left>   . . . .
<tr valign=top><td align=left>iov[iovcount-1].iov_base
<td align=center>x(x)
<td align=center>=(=)
<tr valign=top><td align=left>iov[iovcount-1].iov_len
<td align=center>x
<td align=center>=
<tr valign=top><td align=left>iovcount
<td align=center>x
<td align=center>/
</table>
</pre>
<p>
This function is used in connectionless mode to send a data
unit to another transport user.  The argument 
<I>fd</I>
identifies the local transport endpoint through which data will be
sent, 
<I>iovcount</I>
contains the number of non-contiguous 
<I>udata</I>
buffers and is limited to an implementation-defined value
given by T_IOV_MAX which is at least 16, and 
<I>unitdata</I>
points to a 
<B>t_unitdata</B>
structure containing the following members:
<pre>
<code>
struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
</code>
</pre>
<p>
If the limit on 
<I>iovcount</I>
is exceeded, the function fails with [TBADDATA].
<p>
In 
<B>unitdata</B>,
<I>addr</I>
specifies the protocol address of the
destination user, and 
<I>opt</I>
identifies options that the user
wants associated with this request. The 
<I>udata</I>
field is not
used.  The user may choose not to specify what protocol
options are associated with the transfer by setting the 
<I>len</I>
field of 
<I>opt</I>
to zero.  In this case, the provider may use default options.
<p>
The data to be sent is identified by 
<I>iov[0]</I>
through
<I>iov[iovcount-1]</I>.
<p>
<dl><dt><b>Note:</b>
<dd>The limit on the total number of bytes available
in all buffers passed (that is:
<I>iov(0).iov_len + . . + iov(iovcount-1).iov_len ) </I>
may be constrained by
implementation limits. If no other constraint applies,
it will be limited by [INT_MAX]. In practice, the
availability of memory to an application is likely to
impose a lower limit on the amount of data that can be
sent or received using scatter/gather functions.
</dl>
<p>
By default, 
<i>t_sndvudata()</i>
operates in synchronous mode and
may wait if flow control restrictions prevent the data from
being accepted by the local transport provider at the time
the call is made.  However, if O_NONBLOCK is set (via
<i><a href="t_open.html">t_open()</a></i>
or 
<i><a href="fcntl.html">fcntl()</a></i>),
<i>t_sndvudata()</i>
executes in
asynchronous mode and will fail under such conditions.  The
process can arrange to be notified of the clearance of a
flow control restriction via either 
<i><a href="t_look.html">t_look()</a></i>
or the EM interface.
<p>
If the amount of data specified in 
<I>iov[0]</I>
through
<I>iov[iovcount-1]</I>
exceeds the TSDU size as returned in the 
<I>tsdu</I>
field of the 
<I>info</I>
argument of 
<i><a href="t_open.html">t_open()</a></i>
or 
<i><a href="t_getinfo.html">t_getinfo()</a></i>,
or is
zero and sending of zero octets is not supported by the
underlying transport service, a [TBADDATA] error is
generated.  If 
<i>t_sndvudata()</i>
is called before the destination
user has activated its transport endpoint (see 
<i><a href="t_bind.html">t_bind()</a></i>),
the data unit may be discarded.
<p>
If it is not possible for the transport provider to
immediately detect the conditions that cause the errors
[TBADDADDR] and [TBADOPT], these errors will alternatively
be returned by 
<i><a href="t_rcvuderr.html">t_rcvuderr()</a></i>.
An application must therefore
be prepared to receive these errors in both of these ways.
</blockquote><h4>VALID STATES</h4><blockquote>
T_IDLE
</blockquote><h4>ERRORS</h4><blockquote>
On failure, 
<I>t_errno</I>
is set to one of the following:
<dl compact>

<dt>[TBADADDR]<dd>The specified protocol address was in an
incorrect format or contained illegal information.

<dt>[TBADDATA]<dd>Illegal amount of data.
<ul>

<li>
A single send was attempted specifying a
TSDU greater than that specified in the
<I>info</I>
argument, or a send of a zero byte
TSDU is not supported by the provider.

<li>
<I>iovcount</I>
is greater than T_IOV_MAX.

</ul>

<dt>[TBADF]<dd>The specified file descriptor does not refer to a transport endpoint.

<dt>[TBADOPT]<dd>The specified options were in an incorrect 
format or contained illegal information.

<dt>[TFLOW]<dd>O_NONBLOCK was set, but the flow control
mechanism prevented the transport provider
from accepting any data at this time.

<dt>[TLOOK]<dd>An asynchronous event has occurred on this transport endpoint.

<dt>[TNOTSUPPORT]<dd>This function is not supported by the underlying transport provider.

<dt>[TOUTSTATE]<dd>The communications endpoint referenced by
<I>fd</I>
is not in one of the states in which a call to this function is valid.

<dt>[TPROTO]<dd>This error indicates that a communication
problem has been detected between XTI and
the transport provider for which there is no other suitable XTI error
<I>(t_errno)</I>.

<dt>[TSYSERR]<dd>A system error has occurred during execution of this function.

</dl>
<br>
</blockquote><h4>RETURN VALUES</h4><blockquote>
Upon successful completion, a value of 0 is returned.
Otherwise, a value of -1 is returned and 
<I>t_errno</I>
is set to indicate an error.
</blockquote><h4>SEE ALSO</h4><blockquote>
<i><a href="fcntl.html">fcntl()</a></i>,
<i><a href="t_alloc.html">t_alloc()</a></i>,
<i><a href="t_open.html">t_open()</a></i>,
<i><a href="t_rcvudata.html">t_rcvudata()</a></i>,
<i><a href="t_rcvvudata.html">t_rcvvudata()</a></i>,
<i><a href="t_rcvuderr.html">t_rcvuderr()</a></i>,
<i><a href="t_sndudata.html">t_sndudata()</a></i>.
</blockquote><hr size=2 noshade>
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UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]

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